I think it's not really that ironic, if you consider that the mass exodus was anyways likely to happen, if Amazon had done nothing. So really the only thing that changed, is Amazon trying to make an attempt to stave off the default exodus (which was already being observed/starting); in that sense, by analogy: is pumping water on a fire ironic? The fire is a given, it's already happening, so the water is just a genuine attempt at firefighting (might work, might not).